1. Field of the Invention
The present invention relates to a three-phase integrated gas insulated bus used in a gas insulated switchgear.
2. Description of Prior Arts
As is widely known, a gas insulated switch gear is often used for switching in the electric power system. The main bus of the gas insulated switch gear is configured in a double bus system to ensure a stable supply of power. Further, the main bus is provided in an isolated phase arrangement or integrated three-phase arrangement.
The integrated three-phase arrangement of the main bus is formed in such a way that a three-phase main bus conductor is supported by an insulation spacer to be located at the apex of a triangle in an insulated gas-filled cylindrical bus enclosure. The triangle is normally configured in an isosceles triangle.
In the gas insulated switch gear, a branch bus is led from the three-phase integrated bus. The method for leading a branch bus from a three-phase integrated bus is disclosed, for example, in the Japanese Application Patent Laid-Open Publication No. Sho 55-103023. 
The branch bus led from the three-phase integrated bus must be led in two directions because of the mechanical layout configuration of the gas insulated switch gear. These directions are a vertical direction (upward or downward) or horizontal direction.
In the prior art, the size of the bus enclosure (cross section) is restricted when the branch bus is led in two directions from the three-phase integrated bus from the view point of ensuring a compact configuration of the gas insulated switch gear. So the branch bus is led in one direction and in the other direction from two bus enclosures, respectively.
In the prior art, a branch bus is led in two directions using two bus enclosures. If the main bus is longer, two bus enclosures must be used, imposing restriction on the size of the gas insulated switch gear with the result that a compact product cannot be manufactured.
The object of the present invention is to solve the aforementioned problem and to provide a three-phase integrated gas insulated bus which ensures compact configuration of a gas insulated switch gear, wherein the branch bus is led in two directions from one bus enclosure.
The present invention is characterized as follows: Three vertical outlets are formed in the longitudinal direction of a cylindrical bus enclosure and three horizontal outlets are formed in almost the same axial position as these vertical outlets in the circumferential direction. The three-phase main bus conductors are laid out to ensure that one side of a triangle having the apexes where three-phase main buses are located is approximately parallel to these horizontal outlets. The main bus conductors are extended to the three vertical outlet positions sequentially starting from the main bus of the phase closest to the vertical outlets, and branch buses are led from the tip positions thereof to the vertical outlets and horizontal outlets.
In other words, the present invention is characterized in that a three-phase bus is connected to one of three vertical outlets (vertical outlets) formed in the longitudinal direction of a cylindrical bus enclosure, a two-phase bus is connected to two of them, and a one-phase bus is connected to three of them; and a branch bus is led from the tip of the main bus conductor of each phase.
In the present invention, main bus conductors are connected to the three vertical outlet positions sequentially starting from the main bus closest to the three vertical outlets formed in the longitudinal direction of the cylindrical bus enclosure, and branch buses are led out from the tip positions. This ensures the insulation distance of each phase bus, and further, allows branch buses to be lead out of one bus enclosure in two directions, whereby a compact configuration of a gas insulated switch gear is ensured.